Did a 20% water change on my currently cycling 10-gallon today, and noticed something alarming:
On my reef tanks, I always had a jug of pre-mixed water as well as a jug of R/O water for water changes/top off. These jugs were at room temp. because they just sat there until I needed them. Whenever I did water changes, I never had to worry about the temp dropping too much.
Today I did a water change on my freshwater tank and used tap water. I didn't think about this, but the temp of the tap water is MUCH colder than the tank temp (especially with it being winter). After the water change, my tank temperature instantly dropped about 5 degrees!! Thankfully there are no fish in the tank right now!! That could have been bad!
My question is this: since I only have one jug for siphoning/filling my tank, should I turn on a little of the warm water when doing water changes? I know I shouldn't make it *warm* but at least not freezing cold like it is right now. It seemed like this would be the logical solution, but I wanted to make sure that using water that has been heated would not harm them in any way.
Will this work? What do you do on your tanks to keep from shocking the fish with a drastic temp. change?